1. Field of the Invention The present invention relates to transduction, and, more specifically, to a method of using a magnetostrictive material to achieve high transduction under compression or tension.
2. Description of the Prior Art
Magnetostriction refers to a change in dimensions, often the length, of a magnetic material with a change in its magnetic state. Often, the change in magnetic state results from the application of a magnetic field. By definition, a positive magnetic material expands in the direction of the field upon application of a magnetic field, and a negative material contracts upon application of a field. Alternatively, a change in dimensions of a magnetostrictive material can cause a change in magnetization and thus produce an emf in an adjoining coil. Therefore, a positive or negative magnetostrictive material can act as a transducer or motor, converting between electrical and mechanical energy (or work).
Magnetostrictive materials are commonly operated with a compressive load condition and can sometimes also operate under a tensile load condition. Typically, positive magnetostrictive materials are operated under compression. Likewise, negative materials work optimally under tension. Note that many of the high power active materials available today are brittle and cannot withstand any substantial amount of tensile stress.
Many of the currently available magnetostrictive materials have only nominal magnetomechanical coupling factors (k). (The square of the coupling factor (k2), which is a measure of transduction, is defined as the fraction of the total energy that is transformed from the magnetic state to the mechanical state. Perfect transduction occurs when k equals 1.) For example, nickel has a coupling factor of only about 0.3, indicating only about a 10% transformation from the magnetic state to the mechanical state. Therefore, most magnetostrictive materials achieve low transduction, which affects the efficiency and performance of the transduction device.